Written By: Jessica Stamm, MS CCN, Certified Clinical Nutritionist
Vitamin K is commonly known for its role in blood clotting, but has recently come to light for other exciting benefits. This undercover nutrient works synergistically with vitamin D to fortify calcium in bones and teeth while keeping it from accumulating in blood vessels, muscle tissue or other soft tissue. The term “vitamin K” actually refers to a group of similarly structured nutrients falling into two main categories – K1 and K2. K1 is found in leafy green vegetables and is needed for blood clotting, while K2 is found in animal products and bacterially fermented foods such as sauerkraut and natto. K2 is a potent calcium regulator with diverse roles:
Several Japanese trials have shown K2 to completely reverse bone loss in menopausal women. K2 plays such a crucial role in calcium storage that Japan has approved it as a clinical treatment for osteoporosis!
In children, K2 is vital for growth of bones and proper formation of teeth. Crowding of teeth and tooth decay are linked to K2 deficiency.
K2 is required for the production of myelin, a substance which insulates nerve endings in the brain to ensure proper communication between cells.
K2 keeps blood vessels supple and strong. Signs of weakened blood vessels such as varicose veins and under-eye swelling may improve with increased K2 intake.
Low K2 levels have been linked to kidney stones, particularly the calcium-based variety.
A 2004 study found that people who consume 45 mcg of K2 daily (the amount in 2 servings of grass-fed dairy) lived an average of seven years longer than people getting 12 mcg. The same study also found that increased intake of K2, but not K1, decreased the risk of death from cardiac disease by 57%. A follow-up study found that for each additional 10 mcg of K2 in the daily diet, there was a 9% decrease in heart attack risk.
The best way to obtain K2 is through a balanced diet rich in grass-fed dairy and other pastured animal products. Those on vegan or low-fat diets can obtain small amounts of K2 from fermented vegetables but must rely on their bodies to convert K1 to K2. Healthy gut bacteria are crucial to the conversion process – taking antibiotics can reduce the conversion of K1 to K2 in the gut by up to 74%. Vitamin K is more easily absorbed from fatty foods than from vegetables (as much as two-fold!) but lightly steaming vegetables and eating with oil or butter may improve absorption.
There is no recommended daily intake for K2 specifically, but many healthcare practitioners suggest 50 micrograms (ug) daily for optimal health. In animal products, levels of K2 vary up to 50-fold depending on grass intake and nutrient content of the soil. This makes it crucial to support farmers who prioritize soil quality in their farming practices. Here are a few guidelines to help you obtain optimal levels of K2:
Choose dairy products from grass-fed cows and opt for fermented options when available, since fermentation concentrates K2 levels. A sampling of cheeses reveals:
A 2-ounce portion of Cheddar cheese from grain-fed cows typically contains 6 ug of K2.
The same portion of a minimally fermented cheese such as Brie from grass-fed cows typically contains 31 ug K2, while a grass-fed cheese that has been subjected to longer fermentation such as Gouda typically contains 44 ug!
K2 is fat-soluble, so choose high-fat dairy products when possible. Levels of K2 in dairy fat vary by season, but a general rule is the more naturally yellow the fat, the higher the K2 content, so look for butter and other whole milk products with a golden hue.
Eat gently cooked egg yolks from pastured hens, which contain an average of 16 ug of K2 per yolk versus yolks from hens raised in confinement which contain only 7.8 ug each.
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